Add `/communities` endpoints for App Community CRUD and admin management

[psarando]

These endpoints will mostly be the same as the /teams endpoints, but will operate on a new communities Grouper folder, and communities will not require members apart from admins.

The list of endpoints to be added:

• GET /communities
• POST /communities
• GET /communities/:name
• PATCH /communities/:name
• DELETE /communities/:name
• GET /communities/:name/admins
• POST /communities/:name/admins
• POST /communities/:name/admins/deleter
• GET /admin/communities
• POST /admin/communities
• GET /admin/communities/:name
• PATCH /admin/communities/:name
• DELETE /admin/communities/:name
• GET /admin/communities/:name/admins
• POST /admin/communities/:name/admins
• POST /admin/communities/:name/admins/deleter

[ianmcorvidae]

Gonna be the one to ask the annoying procedural question: should we make a small (go, probably) microservice that terrain delegates to for this group of endpoints?

[psarando]

should we make a small (go, probably) microservice that terrain delegates to for this group of endpoints?

Not at this time. All the current /teams endpoints are already implemented in terrain, and these endpoints are just going to reuse those existing functions, but with minor tweaks, such as Grouper folder name changes.